Who doesn't have trust issues with their hygrometers?!
This may be old news but for those of you who haven't heard of this before, this link shows a very interesting way of calibrating hygrometers:
How to Test a Hygrometer: 6 Steps (with Pictures) - wikiHow
Instead of a ziplock bag I used a tupperware container like in this video:
https://www.youtube.com/watch?v=amSMJ2pUIdE
Note: You need to wait the full 24 hours, as the video says. Not 6 like the wikihow article says.
Here were my results:
I was happy to see I have at least one accurate hygrometer!